The Division of Labor. 29 



suggests the higher forms of life, where the animal 

 or plant is composed, not of one cell, but of many, 

 among which is established a division of labor. 



When the single-celled organism reproduces, it 

 divides and becomes two, as seen in the amoeba. 

 Each division is a complete individual. In the 

 higher forms of life the creature starts as a single 

 cell. Every living thing, even to man himself, sets 

 out on the life journey, as a single cell. This cell 

 divides, but instead of the two cells thus made 

 separating from each other, they stay together. 

 Each of the two cells then divides again, and the 

 group of cells, instead of separating, stays together. 

 The diagram at the bottom of the page may 

 make clearer how the cell is able to build complex 

 forms. There is seen the single cell, then the cell 

 after division, then a simple thimble-like form built 

 of many cells, then a little ani- 

 mal that grows in the sea, in 

 which the cells have assumed 

 several different 

 Ct^^N,-. forms, and final- 



ly a worm-like form in which the creature is but 

 a long tube, with another tube running through 

 the middle. This last form has many different sets 

 of cells doing different work. For, unlike the 



